JPH04201468A - Apparatus for positioning platen - Google Patents

Abstract

PURPOSE:To obtain the title apparatus capable of easily and accurately corresponding to the thickness of a printing medium by providing a cam for moving a platen in the direction of a printing head corresponding to the angle of rotation of a link mechanism through the link mechanism and the reversibly rotatable motor connected to the cam through a friction clutch and transmitting to the cam within the range of definite rotary load. CONSTITUTION:A pulse motor 13 can be reversibly rotated and the torque thereof is transmitted to a rotary shaft through a belt 12 and a friction clutch 10. The friction clutch 10 races by slip when load of a definite value or more acts on the rotary shaft 9. A cam 11 is in contact with the roller 15 provided to a ring 8 in a freely rotatable manner and, when the cam 11 is rotated in a direction A1, the ring 8 is moved left and right to raise a platen 3 and, when the cam 11 is rotated in a direction A2, an energizing member 7 reversely moves the ring 8 to the right and the platen 3 falls.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a platen positioning device for ensuring a constant cap between a print medium and a print head in a printer to achieve stable print quality even if the thickness of the print medium varies.

[Conventional technology]

If a printer that prints on print media of different thickness is a moving print head type in which the platen is fixed and the print head is moved toward and away from the platen depending on the thickness of the print medium, the amount of print head movement Since there is a problem that print quality deteriorates due to the size of the print medium, a printer is disclosed in JP-A-2-130170 in which the platen is first moved coarsely according to the thickness of the print medium, and then the print head is moved slightly. ing. In this printer, a print head is supported by a carrier frame so as to be movable up and down. In addition, a rotating shaft is provided horizontally on the guide leg, and a pair of eccentric cams are provided on this rotating shaft so as to be able to rotate together, and when the eccentric cam is in a downward position, the eccentric cam separates from the bracket of the platen. However, when the eccentric cam 7 is in the upward position, it comes into contact with the bracket and pushes the platen upward. In addition, one end of the rotating shaft is connected to a motor via a friction clutch and gears, and when the platen is pushed up by an eccentric cam and a print medium such as a passbook placed on the platen comes into contact with the print head. , the friction clutch spins idly. After this, the platen descends due to its own weight and is stopped by the locking means at a position where the print head can print.
Printing is performed on the print medium by lowering the print head. Here, when the thickness of the printing medium is small, the amount of movement of the platen is large, and when the thickness of the printing medium is large, the amount of movement of the platen is small.

[Problem to be solved by the invention]

As mentioned above, conventional printers for print media of different thicknesses move the platen relative to the print head, lock the platen in a printable position, and then lower the print head onto the print media. The configuration and control are complicated because the amount of movement of the print head is controlled depending on the thickness of the print medium. In view of the above points, the present invention can be easily configured and controlled;
It is an object of the present invention to provide a platen positioning device that can easily and accurately correspond to the thickness of a print medium.

[Means to solve the problem]

In order to achieve the above object, the platen positioning device according to the present invention is provided with a platen that is movable in a direction toward and away from a print head, and is biased in a direction away from the print head by a biasing member. , a cam that is provided on the opposite side of the platen to the print head and moves the platen toward the print head via a link mechanism in accordance with the rotation angle; It comprises a motor capable of forward and reverse rotation for transmitting rotational force to the cam within the range of rotational load, and the cam is characterized in that it has means for regulating the rotation range in the reverse direction. Further, the link mechanism includes a pair of left and right levers having one end pivotally connected to the platen and rotatably supported at a fulcrum, a link connecting the other ends of both levers, and a link rotatably attached to the link, The device is characterized in that it comprises a roller that is in contact with the circumferential surface of the cam, and that the means for regulating the range of rotation of the cam in the reverse direction is a convex portion that engages with the roller when the platen is at its maximum separation.

[Effect]

In the above configuration, when the motor is rotated in a predetermined direction,
A cam is rotated via a friction clutch, and the rotation of the cam causes the platen to approach the print head via a link mechanism. Since it is stopped when it approaches the platen or print head, a load above a certain level is applied to the friction clutch. This causes the friction clutch to slip and spin idly. After the motor has rotated to a predetermined amount, it is stopped and rotated in the opposite direction by a predetermined amount to ensure a predetermined gap between the print medium and the print head. After printing is completed, the motor is reversed by a predetermined amount, and the platen is moved away from the print head by the reverse rotation of the cam and the biasing member. When the cam is moved away to the maximum retracted position, the reverse rotation regulating means of the cam applies a load above a certain level to the friction clutch, so that the friction clutch idles and thereafter the reverse rotation of the motor is stopped.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings. Figure 1 is a front view, Figure 2 is a plan view, Figure 3 is the same as Figure 2.
-■ line sectional view, and FIG. 4 is a side view. As shown in FIG. 1, a print head 2 is provided on a horizontal guide shaft 1 so as to be movable in the horizontal direction via a carrier 2A. A platen 3 is arranged parallel to the guide shaft 1 and facing the print head 2. One end of an L-shaped lever 4 is pivotally attached to the lower side of both left and right ends of the platen 3. Place the lever 4 at the fulcrum 5 of its bent part.
By rotating around , the platen 3 moves up and down. That is, it moves relative to the print head 2. A biasing member 7 such as a coil spring is provided between the other end of each lever 4 and the fixing member 6 to constantly bias the platen 3 in a direction away from the print head 2. The left and right L-shaped levers 4 are connected by a link 8. The left and right levers 4 and links 8 constitute a link mechanism. A rotating shaft 9 is provided in a direction perpendicular to the platen 3, and a friction clutch 10 and a cam 11 are provided on the rotating shaft. The rotating shaft 9 is connected to the driven side of a friction clutch 10, and a toothed belt 12 is wound around the driving side of the friction clutch, and the toothed belt is connected to a pulse motor 13 which is a driving source.
It is wound on the rotating shaft 14 of. The pulse motor 13 is capable of forward and reverse rotation, and when rotated, transfers its rotational force to the belt 12 and the friction clutch 10.
The signal is transmitted to the rotating shaft via. The friction clutch 10 slips and idles when a load of a certain level or more is applied to the rotating shaft 9. In the example shown in FIG. 1, the cam 11 has an outer circumferential diameter that gradually increases over approximately 180° counterclockwise, and a convex portion 11 at the terminal end.
A is formed. The cam is in sliding contact with a roller 15 rotatably provided on the ring 8, and when the cam 11 rotates in the direction of the solid arrow A1 in FIG. 1, the link 8 is moved left and right and the platen 3 is raised. However, when rotating in the direction of the dotted arrow A2, the biasing member 7 moves the link 8 in the opposite direction to the right, so that the platen 3 descends. The levers 4, 4, link 8 and roller 15 are connected to the cam 1.
This configuration constitutes an example of a motion converting means for converting the rotational motion of the print head of the platen 3 into a movement towards and away from the printing head in two directions according to the rotation angle of the print head. When the print medium is placed on the platen 3 in this manner, the rotating shaft begins to rotate in the direction of the solid arrow A1, and the platen 3 rises until the print medium comes into contact with the print head 2. When they come into contact, the cam 10 presses the roller 15 and a load is applied to the rotating shaft 9, so that the friction clutch 10 is separated from the rotating shaft and idles together with the pulse motor. When the motor rotates until it reaches a predetermined amount or angle, it stops. From this stop position, the pulse motor rotates in reverse by a predetermined amount or a predetermined angle, that is, the platen is lowered to maintain an optimal gap between the print medium and the print head. After printing is completed, the pulse motor 13 rotates a predetermined amount in the direction of the chain arrow A2, the cam 11 rotates in the direction of the chain arrow A2, and the platen 3 is lowered. As the cam rotates, its convex portion 11a hits the roller 10 and its rotation is stopped, so the friction clutch 10 idles. The above embodiment is suitable for cases where the thickness of the print medium is constant over the entire length in the printing direction by the print head 2, such as cut paper or a booklet M printed parallel to the binding line as shown in FIG. This is a configuration example in which the components include one platen 3, one cam 11, one friction clutch 10, and a set of motors 13. In the case of a booklet M2 in which the printing medium is printed in a direction perpendicular to the binding as shown in FIG. 6, the thickness on the left side and the right side of the binding may be different, so the above embodiment cannot cope with this. FIG. 7 shows two left and right sets each containing the platen, link mechanism, cam, and friction clutch described above, each containing the platen, link mechanism, cam, and friction clutch, on both the left and right sides of the printing medium to be conveyed, with the binding line as the border, and - motors 13. transmission belts 12a, 12b. The rotational force is transmitted to each clutch IOA, IOH via the clutch 12c, and each platen 3A, 3B is positioned relative to one print head 2 according to the thickness of the spread part of the booklet placed thereon. You can do it correctly.

【Effect of the invention】

As described above, the platen positioning device according to the present invention is
Consisting of a drive source, a friction clutch, and a motion conversion means, it has a very simple configuration and can be easily installed in a small space, and the friction clutch is activated when the platen reaches its maximum approach position and maximum retraction position. Since the motor is made to idle when a load above a certain level is applied, control is simple and it is easy to secure a gap.

[Brief explanation of the drawing]

Fig. 1 is a front view of an embodiment of the present invention, Fig. 2 is a plan view, Fig. 3 is a sectional view taken along the line ■-■ in Fig. 2, Fig. 4 is a left side view of Fig. 1, and Fig. 5 is a plan view of a kind of double-page spread of printing media,
FIG. 6 is a similar plan view of another type of print medium, and FIG. 7 is a front view of an embodiment applied to the print medium of FIG. 2... Print head, 3... Platen, 4... Lever, 5... Fulcrum, 7... Biasing member, 8... Link, 9... Rotating shaft, 10... Friction clutch, 11...Cam, 11a...Protrusion, 13...Pulse motor. Patent applicant Created by Shinko Seisaku Co., Ltd. Agent Patent attorney Masao Ishii Figure 5 Figure 6

Claims (2)

[Claims] (1) a platen that is movable toward and away from the print head and is biased in a direction away from the print head by a biasing member; a platen that is provided on the opposite side of the print head to the platen; , a cam that moves the platen toward the print head according to its rotation angle via a link mechanism; and a cam that is connected to the cam via a friction clutch and applies rotational force to the cam within a constant rotational load range. A platen positioning device comprising: a motor capable of forward and reverse rotation; and the cam has means for regulating a rotation range in a reverse direction. (2) The link mechanism includes a pair of left and right levers with one end pivotally attached to the platen and rotatably supported at a fulcrum, a link connecting the other ends of both levers, and a link rotatably attached to the link, 2. A roller that is in contact with a circumferential surface of the cam, and the means for regulating the range of rotation of the cam in the reverse direction is a convex portion that engages with the roller when the platen is at its maximum separation. Platen positioning device as described.